Center robotic arm with five-bar spherical linkage for endoscopic camera

ABSTRACT

A robotic arm including a parallel spherical five-bar linkage with a remote center of spherical rotation. The robotic arm movably supports an endoscopic camera. Two outboard links are pivotally coupled together. At least one of the two outboard links supports the endoscopic camera. Two inboard links are respectively pivotally coupled to the two outboard links such that the two inboard links are able to cross over one another. The two inboard links moveably support the two outboard links. A ground link is pivotally coupled to the two inboard links. The ground link moveably supports the two inboard links.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 13/915,564, filedJun. 11, 2013, which is a continuation of application Ser. No.11/623,311, filed Jan. 15, 2007, now U.S. Pat. No. 8,469,945, whichclaims the benefit pursuant to 35 U.S.C. 119(e) of U.S. ProvisionalApplication No. 60/786,491, filed Mar. 28, 2006, and U.S. ProvisionalApplication No. 60/762,233, filed Jan. 25, 2006, each of which is herebyincorporated by reference in its entirety.

FIELD OF INVENTION

The embodiments of the invention relate generally to robotic surgicalsystems. More particularly, the embodiments of the invention relate tolinkage in robotic arms.

BACKGROUND

Minimally invasive surgery (MIS) provides surgical techniques foroperating on a patient through small incisions using a camera andelongated surgical instruments introduced to an internal surgical site,often through trocar sleeves or cannulas. The surgical site oftencomprises a body cavity, such as the patient's abdomen. The body cavitymay optionally be distended using a clear fluid such as an insufflationgas. In traditional minimally invasive surgery, the surgeon manipulatesthe tissues using end effectors of the elongated surgical instruments byactuating the instrument's handles while viewing the surgical site on avideo monitor.

A common form of minimally invasive surgery is endoscopy. Laparoscopy isa type of endoscopy for performing minimally invasive inspection andsurgery inside the abdominal cavity. In standard laparoscopic surgery, apatient's abdomen is insufflated with gas, and cannula sleeves arepassed through small (generally ½ inch or less) incisions to provideentry ports for laparoscopic surgical instruments. The laparoscopicsurgical instruments generally include a laparoscope (a type ofendoscope adapted for viewing the surgical field in the abdominalcavity) and working tools. The working tools are similar to those usedin conventional (open) surgery, except that the working end or endeffector of each tool is separated from its handle by a tool shaft. Asused herein, the term “end effector” means the actual working part ofthe surgical instrument and can include clamps, graspers, scissors,staplers, image capture lenses, and needle holders, for example. The endeffector for the laparoscope may include lenses and light sources thatmay be optically couple to a camera and lamps through the tool shaft. Toperform surgical procedures, the surgeon passes these working tools orinstruments through the cannula sleeves to an internal surgical site andmanipulates them from outside the abdomen. The surgeon monitors theprocedure by means of a monitor that displays an image of the surgicalsite taken from the laparoscope. Similar endoscopic techniques areemployed in other types of surgeries such as arthroscopy,retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy,sinoscopy, hysteroscopy, urethroscopy, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention by way of example and not limitation. Inthe drawings, in which like reference numerals indicate similarelements:

FIG. 1 is a plan view of a surgical suite in which embodiments of theinvention are used.

FIG. 2 is a plan view of a portion of the operating suite of FIG. 1.

FIG. 3 is a side view of a portion of the operating suite of FIG. 2.

FIG. 4A is a schematic view of a parallel five-bar linkage in a firstpose.

FIG. 4B is a schematic view of the parallel five-bar linkage of FIG. 4Ain a second pose.

FIG. 5 is a schematic view of a parallel spherical five-bar linkage.

FIG. 6A is a schematic view of another parallel spherical five-barlinkage in a first pose.

FIG. 6B is a schematic view of the parallel five-bar linkage of FIG. 6Ain a second pose.

FIG. 7A is a pictorial view of an embodiment of the invention in a firstpose.

FIG. 7B is a pictorial view of the embodiment of FIG. 7A in a secondpose.

FIG. 8 is a view of a first side of an embodiment of the invention.

FIG. 9 is a bottom view of the embodiment of the invention shown in FIG.8.

FIG. 10 is view of a second side of the embodiment of the inventionshown in FIG. 8.

FIG. 11 is a top view of the embodiment of the invention shown in FIG.8.

FIG. 12 is an end view of the embodiment of the invention shown in FIG.8.

FIG. 13 is a pictorial view of a portion of the embodiment as shown inFIG. 12.

FIG. 14 is a bottom view of the embodiment of the invention as shown inFIG. 9 in a different operative position.

FIG. 15 is a bottom view of another embodiment of the invention.

FIG. 16 is an end view of another embodiment of the invention.

FIG. 17 is a schematic view of a parallel spherical five-bar linkage.

FIG. 18 is a schematic view of another parallel spherical five-barlinkage.

FIG. 19 is a pictorial view of another embodiment of the invention.

FIG. 20 is a schematic view of the parallel spherical five-bar linkageshown in FIG. 19.

FIG. 21 is a pictorial view of another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description describes the invention as it may be used in alaparoscopic surgery. It is to be understood that this is merely oneexample of the types of surgeries in which the invention may be used.The invention is not limited to laparoscopy nor to the particularstructural configurations shown which are merely examples to aid in theunderstanding of the invention. Traditional minimally invasive surgeryrequires a high degree of surgical skill because the surgeon's handmovements are controlling a surgical tool at a substantial distance fromthe surgeon's hands, often requiring unnatural and non-intuitive handmotions. In robotically assisted surgery, a surgeon may operate a mastercontroller to control the motion of surgical instruments at the surgicalsite. Servo mechanisms may move and articulate the surgical instrumentbased on the surgeon's manipulation of the hand input devices. Therobotic assistance may allow the surgeon to control the motion ofsurgical instruments more easily and with greater precision.

FIG. 1 shows a schematic plan view of a surgical suite in which theinvention may be used. A patient 110 is shown on an operating table 112undergoing robotically assisted laparoscopic surgery. A surgeon 120 mayuse a master controller 122 to view a video image of the internalsurgical site provided by an endoscopic camera, a laparoscopic camera104 in the case of abdominal surgery, and control one or more surgicalinstruments and the endoscopic camera by means of robotic servomechanisms. The master controller 122 will typically include one or morehand input devices (such as joysticks, exoskeletal gloves, or the like)which are coupled by a servo mechanism to a surgical instrument.

A robotic arm 116 that embodies the invention may be used to support andmove the laparoscopic camera 104 at the surgical site during roboticallyassisted surgery. It is desirable to support the laparoscopic camera 104such that the tool shaft 118 of the instrument and the cannula 106through which it passes pivot about a center of spherical rotationpositioned in space along the length of the tool shaft and cannula.Additional robotic arms 100, 102 may support and move surgicalinstruments. The robotic arms 100, 102 for supporting the surgicalinstruments may be of a different form than the robotic arm 116 forsupporting the laparoscopic camera.

Each robotic arm 100, 102, 116 may be supported by an articulated set-uparm 130, 132, 134. The set-up arms may be attached to the operatingtable 112. Each set-up arm may include a number of segments coupled byjoints that provide one or more degrees of freedom that allow therobotic arm to be positioned within a defined range of motion. One ormore locking mechanisms may be provided to fix the segments and jointsof the set-up arm when the robotic arm is in the desired position. Theset-up arms may allow the robotic arms 100,102, 116 to be fixed at anarbitrary position with respect to the operating table and the patientthereon. Joint angle sensors may be provided on the set-up arm to allowthe pose of the set-up arm and the resulting position of the supportedrobotic arm to be determined.

Each robotic arm 100, 102, 116 may be fixed at a position where thecenter of spherical rotation is substantially at the access point to theinternal surgical site (for example, with the incision that providesentry for the trocar or cannula 106 at the abdominal wall duringlaparoscopic surgery). An end effector of the surgical instrument 104supported by the robotic arm 116 can be positioned safely by moving theproximal end of the tool shaft 118 with the robotic arm 116 withoutimposing dangerous forces against the abdominal wall.

Each robotic arm 100, 102, 116 will support one surgical instrumentwhich may be detachable from the robotic arm. While a variety ofsurgical instruments 108 may replace the surgical instrument on therobotic arm 100, 102 during the course of a single surgery, thelaparoscopic camera 104 is generally left in place throughout the courseof a surgery. Each robotic arm 116 may support a cannula 106 that passesthrough an incision into the body of the patient 110. The tool shaft 118of the surgical instrument or laparoscopic camera 104 passes through thecannula 106 to the internal surgical site.

The robotic arm 116 may support the laparoscopic camera 104 such thatthe cannula 106 and the tool shaft 118 of the instrument pivot about acenter of spherical rotation positioned in space along the length of thecannula 106. The center of spherical rotation may also be called theremote center of spherical rotation because it is the spherical centerof rotational motion for the robotic arm while being spaced apart fromthe structure of the robotic arm. Motion about the center of sphericalrotation may be described as spherical motion because a point at aradial distance from the center of spherical rotation will move on aspherical surface having the radial distance as its radius. The cannula106 defines an insertion axis that passes through an access point, suchas an incision in the abdominal wall of the patient 110, to the internalsurgical site. The tool shaft 118 extends along the insertion axis.

Each robotic arm 100, 102, 116 may include one or more servo motors tomove the arm to a desired position. Each robotic arm may include one ormore additional servo motors to move the surgical instrument orlaparoscopic camera 104 and/or an end effector on the surgicalinstrument or laparoscopic camera. One or more control cables 124 mayprovide signals between the computer 123 in the master controller 122and the servo motors of the robotic arms 100, 102, 116. The mastercontroller 122 may include a computer 123 to provide signals thatcontrol the servo mechanisms of the robotic arms, the surgicalinstruments, and laparoscopic camera based on the surgeon's input andreceived feedback from the servo mechanisms.

FIG. 2 shows an enlarged view of a portion of FIG. 1 including thepatient 110 and the robotic arms 100, 102, 116. FIG. 3 shows an sideview of the robotic arm 116 that supports and moves the laparoscopiccamera looking from the patient's left hand side. A schematiccrosssection of the patient 110 is shown in the area where the cannula106 is inserted through an incision 314 in the abdominal wall. The toolshaft 118 of the laparoscopic camera 104 may be seen emerging from theend of the cannula 106 internal to the patient 110. An end effector 300at the distal end of the tool shaft 118 may provide lenses and lightsources. The lenses and light sources may be optically coupled to acamera and lamps through the tool shaft. The camera and lamps may besupported by the robotic arm 116 at a proximal end of the tool shaft.

The robotic arm 116 includes a spherical linkage to support thelaparoscopic camera, as will be discussed in greater detail below. Thespherical linkage constrains the motion of the insertion axis torotation about a remote center of spherical rotation 306 which may belocated along the length of the cannula 106. By locating the remotecenter of spherical rotation 306 at or near the incision 314, theinsertion axis may be moved without significant lateral motion at theincision.

The end effector 300 is passed through the cannula 106 to the internalsurgical site along the insertion axis. The end effector 300 issupported by the tool shaft 118 and coupled to one or more of cameras,lamps, and servo mechanisms through the tool shaft. Translation of theend effector 300 may be accomplished by translation of the laparoscopiccamera 104 with the tool shaft 118 and attached end effector.

The end effector 300 may be moved in two additional dimensions by movingthe tool shaft 118 about its remote center of spherical rotation 306.The robotic arm 116 will control these two dimensions of motion bymoving the tool shaft 118 to change its angular position in space. Themotion of the tool shaft 118 may be described in terms of the positionof the insertion axis in a spherical coordinate system. A point in spacemay be specified in terms of two angles and a distance from a center ofa spherical coordinate system. It will be appreciated that only the twoangles are necessary to specify an insertion axis that passes throughthe center of the spherical coordinate system.

The robotic arm 116 of the present invention includes a parallelspherical five-bar linkage to move and support the laparoscopic camera104 such that the tool shaft 118 of the instrument pivots about a remotecenter of spherical rotation 306 positioned in space along the insertionaxis and generally along the length of the cannula 106.

FIG. 4A shows a simplified, 2-dimensional schematic diagram of aparallel five-bar linkage 400. This example illustrates the linkageoperating in essentially a flat plane. The inventive linkage operatessimilarly in 3-dimensional space and will be described subsequently. Aparallel five-bar linkage is a system of four rigid bars or links 401,402, 403, 404 pivoted to each other and to a fixed base link 405. Thefixed base link may be referred to as the ground link. It is to beunderstood that the ground link 405 is fixed only in the sense that itprovides a fixed frame of reference for the remaining four links. Theground link 405 may be positioned in space to move the entire five-barlinkage 400.

Each link includes two pivot axes. In the present invention, there is asubstantial distance between the two pivot axes on each link. All of thepivot axes 411, 412, 413, 414, 415 are perpendicular to a commonsurface. The links are coupled at the pivot axes such that the links canrotate relative to each other about the pivot axis at which they arecoupled. The rotatable coupling of the links at a pivot axis can takeany of a variety of forms that limits the motion of the coupled links torotation about the pivot axis. A number of axes are described for theparallel spherical five-bar linkage. The term “axis” may be usedinterchangeably to refer to a “joint” or a “pivot” except for theinsertion axis.

The ground link 405 provides two inboard axes 412, 413. An inboard link401, 404 is pivotally coupled to each of the inboard axes 413, 412. Eachinboard link 401, 404 has an intermediate axis 414, 411 spaced apartfrom the inboard axis 413, 412. Each inboard link 401, 404 is pivotallycoupled to an outboard link 402, 403 at the intermediate axis 414, 411.Each outboard link 402, 403 has an outboard axis 415 spaced apart fromthe intermediate axis 414, 411. The two outboard links 402, 403 arepivotally coupled together at the outboard axis 415. The outboard axis415 can be positioned perpendicular to the common surface (in this2-dimensional illustrative example) anywhere within its range of motionthus providing an endpoint motion at the outboard axis 415 with twodegrees of freedom. If motors are provided to rotate each of the inboardlinks 401, 404 about their inboard axis 413, 412, as suggested by thearrows, the outboard axis 415 may be positioned anywhere within itsrange of motion by rotating the two inboard links with the motors.Conversely, movement of the outboard axis 415 within its range of motiontranslates into rotation of the two inboard links 401, 404 about theirinboard axis 413, 412.

A linkage that couples rotation of two ground-referenced independentlinks with two dimensional movement of an axis is a parallel linkage.The rotary motion provided by the two motors to the two inboard linksmay be described as parallel rotary motion inputs. It should be notedthat “parallel” is used here to indicate two inputs that are providedindependently of one another and not in the geometric sense to indicatethe direction of the inputs. In a parallel linkage, the two independentparallel inputs act upon the same body at some distal point where linkscoupled to the inputs join to drive the same object or link.

It will be appreciated that there are two possible positions for each ofthe inboard links 401, 404 in a five-bar linkage for most of thepossible positions of the outboard axis. For example, the inboard links401, 404 could also be positioned as indicated by the dashed lines 401′,404′. These positions for the inboard links are generally consideredundesirable because the distance between the intermediate axes 414′,411′ is reduced and the angle between the outboard links 402′, 403′ isreduced. It is normally desirable to maximize the distance between theintermediate axes to provide a broad base of support for the outboardaxis 415. It is also normally desirable to have the outboard links 402′,403′ as close to being at right angles to one another as possible tosupport the outboard axis 415. While the conventional configuration of afive-bar linkage provides good structural support for the outboard axis415, the resulting structure requires a substantial amount of space inwhich to move. The alternative configuration as indicated by the links401′, 402′, 403′, 404′ drawn with dashed lines occupies a smaller area(as projected onto the plane) and is therefore a more compact mechanicalconfiguration.

FIG. 4B shows the parallel five-bar linkage 400 after the inboard links401, 404 have been rotated in a counter-clockwise direction. It may beseen that the outboard axis 415 has been moved generally to the left bythe rotation of the inboard links 401, 404. The same position of theoutboard axis 415 may also be produced by a similar rotation of theinboard links 401′, 404′ when the parallel five-bar linkage 400 is inthe compact mechanical configuration illustrated by the dashed lines.

A spherical linkage for the purposes of this description is a3-dimensional version of the 2-dimensional mechanical linkage describedabove. In the 3-dimensional linkage, all pivot axes pass through acommon remote center of spherical rotation. “Pass through” includes axesthat may be slightly displaced (due to slight errors in manufacturing ofthe physical links, for example) from the remote center of sphericalrotation to accommodate the structural limitations of the robotic armwhere the displacement is small enough that the linkage hassubstantially the same kinematics (characteristic motions) as if theaxes actually included the precise, theoretical remote center ofspherical rotation. Note that axes that pass through a remote center ofspherical rotation are also perpendicular to a spherical surfacecentered on the remote center of spherical rotation.

FIG. 5 shows a schematic diagram of a parallel spherical five-barlinkage 500. As with the previously discussed planar five-bar linkage,the parallel spherical five-bar linkage 500 is a system of four rigidlinks 501, 502, 503, 504 pivoted to each other and to a fixed base orground link 505. When a parallel five-bar linkage is constructed in aspherical form, all of the pivot axes 511, 512, 513, 514, 515 areperpendicular to a common spherical surface and therefore pass through aremote center of spherical rotation 520 of the common spherical surface.In particular, the outboard axis 515 will always pass through the remotecenter of spherical rotation 520 within its range of motion. Thus, aparallel spherical five-bar linkage 500 provides the desired constrainedmotion for a surgical instrument such that the tool shaft of theinstrument pivots about a remote center of spherical rotation whensupported and moved by the outboard axis 515 of the linkage 500. Themotors to move the surgical instrument are placed at the inboard axes513, 512 of the ground link 505. This avoids the need to move one motorwith the other motor as might be required if a serial arm mechanism wereused.

As shown schematically in FIG. 6A, it has been discovered that aparallel spherical five-bar linkage 600 can be constrained so that theintermediate axes 614, 611 do not assume the conventional configurationwhere the intermediate axes are at their maximum possible separationand, surprisingly, provide good structural support for the outboard axis615. This results in a more compact configuration that is better suitedfor use as a robotic arm to support an endoscopic camera where it isoften necessary to have other robotic arms in close proximity within alimited amount of space as shown by the exemplary system in FIGS. 1 and2.

The parallel spherical five-bar linkage 600 shown schematically includesa ground link 605, two inboard links 601, 604 pivotally coupled to theground link, and two outboard links 602, 603 pivotally coupled to eachother at one end and to the two inboard links 601,604 respectively at anopposite end. The first inboard link 601 is pivotally coupled to theground link 605 at a first axis of rotation 613. The first inboard link601 further includes a first intermediate axis 614 at a first distancefrom the first axis of rotation 613. A first outboard link 602 ispivotally coupled to the first inboard link 601 at the firstintermediate axis 614. The first outboard link 602 has an outboard axis615 at a second distance from the first intermediate axis 614.

The second inboard link 604 is pivotally coupled to the ground link at asecond axis of rotation 612. The second inboard link 604 has a secondaxis of rotation 612 that is separated from the first axis of rotation613 by a fourth distance. The second inboard link 604 further includes asecond intermediate axis 611 at a fifth distance from the second axis ofrotation 612. A second outboard link 603 is pivotally coupled to thesecond inboard link 604 at the second intermediate axis 611 and to thefirst outboard link 602 at the outboard axis 615. The outboard axis 615is at a sixth distance from the second intermediate axis 611.

A mechanical stop may limit the rotation of the outboard links 602, 603about the outboard axis 615 such that a minimum angle is maintainedbetween the outboard links, perhaps a minimum angle in the range of 15to 30 degrees. The links are assembled and constrained such that whenthe outboard axis 615 lies in a plane 622 that is the perpendicularbisector of the line segment from the first axis of rotation 613 to thesecond axis of rotation 612, each of the inboard links 601, 604intersects 624 the bisecting plane 622. (The double dashed lines areintended to suggest an edge of the portion of the imaginary bisectingplane 622 in the vicinity of the linkage 600. The dashed circleindicates the point of intersection between each of the inboard links601, 604 and the bisecting plane 622, which is at the same place for theconfiguration and pose shown.) When an inboard link intersects thebisecting plane, the axis of rotation and the intermediate axis will lieon opposite sides of the plane. It will be appreciated that thisrequires the inboard links 601, 604 to be able to cross over oneanother.

A specific position assumed by a robotic arm may be referred to as apose. Placing a robotic arm in a specific position may be referred to asposing the robotic arm. The parallel spherical five-bar linkage may belimited in its motion such that the two intermediate axes 614, 611 arerelatively close together compared to the maximum separation possiblefor any given pose of the robotic arm 600. In particular, each inboardlink 601, 604 may be in one of two positions for a given position of theoutboard axis 615, except for the singularities where the axis ofrotation 612, 613, the intermediate axis 611, 614, and the outboard axis615 are coplanar. One of the two positions for each of the two inboardlinks 601, 604 will provide the maximum distance between theintermediate axes 611, 614. The pose where each of the two inboard links601, 604 is in the other of the two positions will be described as thecompact pose. It will be appreciated that this always results in lessthan the maximum distance between the intermediate axes 611, 614although it may not result in the minimum possible distance. If theoutboard links are constrained to maintain at least a minimum anglebetween the outboard links and the parallel five-bar spherical linkageis assembled in a compact pose, then the linkage will be limited to arange of compact poses.

FIG. 6B shows the parallel spherical five-bar linkage 600 after one ofthe inboard links 601 has been rotated in a counter-clockwise direction.It may be seen that the outboard axis 615 has been moved generally tothe left by the rotation of the inboard link 601. It may also been seenthat points on the outboard axis 615 are constrained to move on aspherical surface. In the pose shown in FIG. 6B neither of the twoinboard links 601, 604 intersect the bisecting plane 622. It will beobserved that the linkage 600 retains the compact configuration eventhough it has moved away from the pose where the outboard axis 615 liesin a plane 622 that is the perpendicular bisector of the line segmentfrom the first axis of rotation 613 to the second axis of rotation 612.

Referring now to FIG. 7A, the inboard links 701, 704 and the outboardlinks 702, 703 are illustrated for the embodiment shown in FIGS. 1-3.The ground link, which is provided by a motor assembly, is not shown inFIG. 7 to allow the relationship between the four moving links to bebetter seen. The two inboard links 701, 704 each can rotate about one ofthe axes of rotation 713, 712. Each inboard link 701, 704 is pivotallycoupled to an outboard link 702, 703 at an intermediate axis 711, 714.The two outboard links 702, 703 are pivotally coupled together at anoutboard axis 715. The outboard axis 715 may also be the insertion axison which the cannula (not shown) is centered.

In some embodiments, the first axis 713 and second axis 712 of rotationare driven by motors connected to a controller that provides signals tothe motors. A first motor may rotate the first inboard link 701 and asecond motor may rotate the second inboard link 704. The controller maylimit the motion of the links so that the parallel five-bar sphericallinkage is limited to a range of compact poses. The controller may limitthe motion of the inboard links 701, 704 such that each of the inboardlinks 701, 704 intersects a perpendicular bisecting plane of the linesegment from the first axis of rotation 713 to the second axis ofrotation 712 when the outboard axis 715 lies in the bisecting plane.When an inboard link intersects the bisecting plane, the axis ofrotation and the intermediate axis will lie on opposite sides of thebisecting plane. The controller may also limit the rotation of theinboard links 701, 704 such that a minimum angular distance ismaintained between the intermediate axes 711, 714, perhaps a minimumangular distance in the range of 15 to 30 degrees. The controller canprovide the same constraint on the range of motion of the links 701-704as a mechanical stop that limits the angle between the outboard links702, 703 at the outboard axis 715.

The parallel spherical five bar linkage may be used to move the outboardaxis 715 to a desired position by controllably rotating the inboardlinks 701, 704, such as by use of a servo motor or stepper motor. FIG.7B illustrates the parallel spherical five bar linkage after one of theinboard links 701 has been rotated in a counter-clockwise direction. Theposes of the parallel spherical five bar linkage shown in FIGS. 7A and7B are generally similar to the poses of the parallel spherical five barlinkage shown schematically in FIGS. 6A and 6B respectively.

In another embodiment, the parallel spherical five bar linkage may beused to sense a position of the outboard axis by determining thebearings of the two inboard axes that result from manipulation of theoutboard axis. For example, rotary encoders, or other sensors, may beplaced at the first 713 and second 712 axis of rotation of the parallelspherical five bar linkage illustrated by FIG. 7. The controller may bereplaced by a computer coupled to the two rotary encoders to receive thebearing of each of the inboard links 701, 704. The computer may thencompute the position of the outboard axis, which may be manipulated byan operator to provide a position input. It will be appreciated that theoutboard axis is constrained to rotate about the remote center ofspherical rotation 720 of the spherical linkage. Thus, the parallelspherical five bar linkage may also be used in the control console 122of FIG. 1 to receive position input for the outboard axis 715 from thesurgeon 120. The position input will have the same constrained motion asthe outboard axis of the robotic arm 116.

Referring now to FIGS. 8, 9, 10, 11, and 12, orthogonal views are shownfor four sides and an end of the robotic arm 116 used to support thelaparoscopic camera in the same pose as shown in FIGS. 1-3. FIG. 8 is afirst side view. FIG. 9 is a bottom view. FIG. 10 is a second side viewof the side opposite the first side. FIG. 11 is a top view. FIG. 12 is aview of the end that is to the right in FIGS. 8-11.

FIGS. 8-12 show a robotic arm 116 that embodies the invention. Therobotic arm includes a motor assembly 800 that serves as a ground linkand four movable links 701, 702, 703, 704 to provide a parallelspherical five bar linkage. The relationship of the four movable linkswas discussed above in connection with FIG. 7. The motor assembly 800provides two rotatable shafts 802, 804. Each of the rotatable shafts iscoupled to one of the two inboard links 701, 704 at one of the axes ofrotation 713, 712 (shown in FIG. 7). A cannula 106 is supported by thetwo outboard links 702, 703 in a position that is coaxial with theoutboard axis 715 (shown in FIG. 7). In this embodiment, the outboardaxis 715 is coincident with the insertion axis for the tool shaft of anendoscopic camera.

FIG. 13 shows the robotic arm 116 of FIG. 12 with the two outboard links702, 703 removed so that the relationship between the motor assembly 800and the two inboard links 701, 704 can be seen. The motor assembly 800and the two inboard links 701, 704 are shaped and coupled in aconfiguration that allows the two inboard links to pass over one anotherand the motor assembly. It may be seen that the two rotatable shafts802, 804 emerge from the motor assembly 800 in substantially oppositedirections in this embodiment. The two rotatable shafts 802, 804 may bedriven by motors coupled to the shafts through right angle drives, suchas a worm and helix drive.

One inboard link 701 moves within a spherical “shell” that is closer tothe center of spherical motion than the motor assembly. The otherinboard link 704 moves within a spherical “shell” that is further fromthe center of spherical motion than the motor assembly. The motorassembly 800 lies between these two spherical “shells.” Thus one pair oflinks passes the motor assembly to the inside and the other pair oflinks passes to the outside.

FIG. 14 shows the robotic arm 116′ of FIG. 9 in a pose with the outboardaxis 806 close to the motor assembly 800. (The motor assembly 800 isdrawn as though transparent as suggested by the dashed lines to allowthe configuration of the movable links 701′, 702′, 703′, 704′ to beseen.) One inboard link 701′, which is coupled to a first rotatableshaft 802 that extends toward the remote spherical center, and thecoupled outboard link 702′ have passed to the inside of the motorassembly 800. These links lie between the motor assembly 800 and theremote spherical center. The other inboard link 704′, which is coupledto a second rotatable shaft 804 that extends away from the remotespherical center, and the coupled outboard link 703′ have passed to theoutside of the motor assembly 800. The motor assembly 800 lies betweenthese links and the remote spherical center.

FIG. 15 shows another robotic arm 1500 that embodies the invention. Themotor assembly includes two motors 1502, 1504 that are coupled by asupport 1506 at a substantial distance from the two axes of rotation1508, 1510. The motor assembly provides the ground link for the parallelspherical five bar linkage. This configuration of the support 1506 maypermit the outboard axis 1512, which may also be the axis for thecannula 1514, to pass between the two axes of rotation 1508, 1510 andthe two motors 1502, 1504 to provide a greater range of motion.

FIG. 16 shows still another robotic arm 1600 that embodies theinvention. The motor assembly includes two motors 1602, 1604 that arecoupled by a support 1606 to provide the ground link for the parallelspherical five bar linkage. The two axes of rotation 1608, 1610 maycoincide with axes of the two motors 1602, 1604 such that a right angledrive is not required. At least one of the inboard links 1614 has anangular length that is substantially less than the angular distancebetween the two axes of rotation 1608, 1610. This permits the inboardlink 1614 to the motor 1604 that is coupled to the other inboard link1616. The other inboard link 1616 may or may not have an angular lengththat is substantially less than the angular distance between the twoaxes of rotation 1608, 1610 as it may be configured to pass to theinside of the motor 1602, between the motor and the remote sphericalcenter, that is coupled to the shortened inboard link 1614.

FIG. 17 shows a schematic representation of a robotic arm 1700 that issimilar to the robotic arm 1600 shown in FIG. 16. A first pair ofinboard and outboard links 1701, 1702 are pivotally coupled at a firstintermediate axis 1714. A second pair of inboard and outboard links1704, 1703 are pivotally coupled at a second intermediate axis 1711. Thetwo outboard links 1702, 1703 are pivotally coupled at an outboard axis1715. One of two motors 1733, 1734 is coupled to each of the inboardlinks 1701, 1704 to rotate the inboard link about an axis of rotation1713, 1712. The two motors are coupled by a ground link 1705 to completethe parallel spherical five-bar linkage.

It may be observed that the first pair of inboard and outboard links1701, 1702 may be constructed so that they move within a first sphericalshell 1736. The second pair of inboard and outboard links 1704, 1703move within a second spherical shell 1738 that is not shared with thefirst spherical shell 1736 except in the vicinity of the outboard axis1715. This arrangement permits the inboard links 1701, 1704 to crossover one another. The inboard links 1701, 1704 in this arrangement mayalso pass to the inside, closer to the remote center of sphericalrotation 1720, of the ground link 1705 that couples the two motors 1733,1734 if the ground link lies outside the second spherical shell 1738.

The arrangement of the linkage 1700 has the further characteristic thatwhen the first inboard link 1701 lies in the same plane as the groundlink 1705 as shown, a first directional vector 1721 from the first axisof rotation 1713 to the first intermediate axis 1714 has the samedirection as a second directional vector 1722 from the first axis ofrotation 1713 to the second axis of rotation 1712. Likewise, when thesecond inboard link 1704 lies in the same plane as the ground link 1705,a third directional vector 1723 from the second axis of rotation 1712 tothe second intermediate axis 1711 has the same direction as a fourthdirectional vector 1724 from the second axis of rotation 1712 to thefirst axis of rotation 1713.

FIG. 18 shows a schematic representation of a robotic arm 1800 that issimilar to the robotic arm 116 as shown in FIG. 11. A first pair ofinboard and outboard links 1801, 1802 are pivotally coupled at a firstintermediate axis 1814. A second pair of inboard and outboard links1804, 1803 are pivotally coupled at a second intermediate axis 1811. Thetwo outboard links 1802, 1803 are pivotally coupled at an outboard axis1815. One of two motors 1833, 1834 is coupled to each of the inboardlinks 1801, 1804 to rotate the inboard link about an axis of rotation1813, 1812. The two motors are coupled by a ground link 1805 to completethe parallel spherical five-bar linkage.

In the arrangement shown in FIG. 18, the ground link 1805 is between thetwo inboard links 1801, 1804 when all three links are in the same plane.The first pair of inboard and outboard links 1801, 1802 may move withina first spherical shell 1836. The second pair of inboard and outboardlinks 1804, 1803 may move within a second spherical shell 1838 that isnot shared with the first spherical shell 1836 except in the vicinity ofthe outboard axis 1815. If the ground link is within a third sphericalshell 1837 that lies between the first and second spherical shells, thenthe inboard links 1801, 1804 may cross over one another and also crossover the ground link. The arrangement of the linkage 1800 has the samedirectionality characteristic when the inboard links 1801, 1804 lie inthe same plane as the ground link 1805 as discussed above for thelinkage 1700 shown in FIG. 17.

In the arrangement shown in FIG. 18, the axes of the motors 1833, 1834may be perpendicular to the axes of rotation 1813, 1812. This may bedone to allow all or part of the motors to be within the third sphericalshell 1837 over which the inboard links 1801, 1804 may pass. A driveshaft 1840, 1842 may couple the motors 1833, 1834 to inboard links 1801,1804 by means of a right angle drive 1844, 1846. In other embodiments,the drive shaft may be coupled to the motors in other arrangements or bea coaxial extension of the motor shaft. The end of the drive shaft 1840,1842 coupled to the motors 1833, 1834 may be described as the drivenend. In the arrangement shown, it may be observed that a first driveshaft 1840 extends from the driven end toward the remote center ofspherical rotation 1820 and a second drive shaft 1842 extends from thedriven end away from the remote center of spherical rotation 1820.

FIG. 19 shows a parallel spherical five-bar linkage 1900 that embodiesthe invention with a structure similar to the robotic arm 116 shown inFIGS. 7-12. FIG. 20 shows a schematic view of the parallel sphericalfive-bar linkage 1900 of FIG. 19. Five pivot axes 1911-1915, about whichthe four movable links 1901-1904 rotate, all pass through a commonremote center of spherical rotation 1920. The first inboard link 1901and the second inboard link 1904 may be coupled to motors that canrotate the inboard links about the first 1913 and second 1912 axes ofrotation. The two motors may be coupled together to form the fifth link(not shown), which is the ground link.

The movable links 1901, 1902, 1903, 1904 are shown as having a generallyarcuate form. It will be appreciated that the links may have any desiredform without affecting the function of the invention. The linkage willfunction as a spherical linkage as long as the axes of the pivotedconnections 1921, 1922, 1923, 1924, 1925 all pass substantially througha common remote center of spherical rotation 1920. Any of the links mayhave an irregular shape, which may include arcuate segments, toaccommodate placement of the pivoted connections such that the links andpivots can pass one another. It will be appreciated that the form of thelinks is unimportant as long as they support the pivot axes such thatthey pass substantially through the remote center of spherical rotation1920.

In the compact configuration of the inventive parallel spherical fivebar linkage, it may be desirable to configure the linkage such that thefirst pair of links 1901, 1902 coupling the first axis of rotation 1913to the outboard axis 1915 can freely pass the second pair of links 1904,1903 coupling the second axis of rotation 1912 to the outboard axis1915. Since the only requirement of the parallel spherical five-barlinkage is that all the pivot axes pass substantially through the commonremote center of spherical rotation 1920, the first pair of links 1901,1902 and the first intermediate pivot 1914 may be configured so that afirst volume swept out by the first pair does not intersect a secondvolume swept out by the second pair of links 1904, 1903 and the secondintermediate pivot 1911. The only connections between the first andsecond volumes are in the vicinity of the outboard axis 1915 and theground link 1905. The form of the links in the embodiment illustrated byFIGS. 19 and 20 are an example of a configuration that permits the firstpair of links 1901, 1902 to pass the second pair of links 1904, 1903.

FIG. 21 shows another embodiment of a parallel spherical five-barlinkage 2100 for a robotic arm including two inboard links 2101, 2104,two outboard links, and a ground link provided by the motor assembly2105. In comparison with the linkage 1900 of FIG. 19, the parallelspherical five-bar linkage 2100 includes an outboard link 2103 having aninsertion axis 2119 that is spaced apart from the outboard axis 2115 byan offset distance. Ideally the insertion axis 2119 is coincident withthe outboard axis 2115. Mechanical packaging advantages can be obtained,however, by separating the insertion axis 2119 from the outboard axis2115.

Preferably the insertion axis 2119 will be placed on the outboard link2103 further from the intermediate axis 2111 than the outboard axis2115. As long as the insertion axis 2119 is perpendicular to the surfaceof the sphere centered on the remote center of spherical rotation 2120and therefore passes through the remote center of spherical rotation2120, then the insertion axis will have the same kinematiccharacteristics as the pivot axes 2111-2115 of the parallel sphericalfive-bar linkage 2100. That is, the insertion axis 2119 will moverelative to the remote center of spherical rotation 2120. The insertionaxis 2119 may or may not lie in the plane defined by the intermediateaxis 2114 and the outboard axis 2115.

The placement of the insertion axis 2119 outboard from the pivot axes ofthe parallel spherical five-bar linkage may allow the endoscopic camera(not shown) to be supported and manipulated without interfering with themotion of the linkage 2100. It may also simplify the construction,installation, removal, and sterile boundary construction of the cannula2106 and its associated mechanical attachment means.

In some embodiments having a spaced apart insertion axis, such as theone illustrated in FIG. 21, the insertion axis 2119, the outboard axis2115, and the intermediate axis 2111 may be coplanar. This arrangementmay simplify the relationship between the positions of the two inboardlinks 2101, 2104 and the position of the outboard axis 2115. Note thatthe insertion axis 2119 can be placed on either of the two outboardlinks 2102, 2103.

The parallel spherical five-bar linkage of the invention may bedescribed using spherical geometry, which is a plane geometry on thesurface of a sphere. While the links of the inventive linkage need notlie of the same spherical surface, or any spherical surface, they can beprojected onto a common spherical surface for the purpose of describingthe linkage. In spherical geometry, distances may be measured as anglesbecause the geometric relationships on the spherical surface areunaffected by changing the radius of the sphere. Angular distanceremains the same regardless of the radius of the sphere.

Navigation on the surface of the Earth is a common example of sphericalgeometry. Latitude and longitude as used in global navigation are afamiliar system for describing locations and directions in a sphericalsystem. The equator defines the points at 0° latitude. The north poledefines 90° latitude and the south pole defines −90° latitude. Longitudeis the angular distance on a circle of constant latitude from anarbitrarily defined line of 0° longitude. Longitude is conventionallyexpressed as being in the range 180° west to 180° east of the 0°longitude line. Bearings are lines of direction from a point expressedas the angle between the bearing and a line of direction to the northpole. Westerly bearings can be expressed as positive angles and easterlybearings can be expressed as negative angles. The following is adescription of an embodiment of the invention expressed in terms of aspherical geometry.

Referring again to FIG. 6, the first axis of rotation 613 of the firstinboard link 601 will be considered as being at 0° latitude and 0°longitude. The second axis of rotation 612 of the second inboard link604 is shown as being at the same latitude and at a positive (easterly)longitude. The second axis of rotation 612 may be at a fixed position of55° longitude and 0° latitude, for example. Thus, in this example theground link has an angular length of 55°. It should be remembered that afixed position means fixed within the frame of reference of thespherical geometry of the linkage and that the entire linkage with itsframe of reference may be freely positioned in space.

All of the movable links 601-604 may have the same angular length as theground link. For example, the first intermediate axis 614 may be spacedapart from the first axis of rotation 613 by 55°. The first outboardaxis 615 may be spaced apart from the first intermediate axis 614 by55°. The insertion axis 619 may be spaced apart from the outboard axis615 by 30°. The second intermediate axis 611 may be spaced apart fromthe second axis of rotation 612 by 55°. The second intermediate axis 611may be spaced apart from the outboard axis 615 by 55°.

The range of rotation of the inboard links 601, 604 about the axes ofrotation 613, 612 may constrained such that a minimum angle of 15° ismaintained between the outboard links 602, 603, for example. The rangeof rotation of the inboard links 601, 604 may further constrained suchthat when the outboard axis 615 has a longitude of 27.5°, for example,the first inboard link 601 has a negative (easterly) bearing and thesecond inboard link 604 has a positive (westerly) bearing. The linesegment that most directly connects the axis of rotation 613, 612 to theintermediate axis 614, 611 on the common spherical surface will crossthe longitude line of the outboard axis 615 for both of the inboardlinks. Thus, the inboard links will cross one another when the outboardaxis is at or near the center of its east-west range of motion. Theconstraints on the rotation of the inboard links prevents them fromuncrossing when the outboard axis is in the central portion of itseast-west range of motion.

These dimension are merely by way of example. The invention may bepracticed with linkages having substantially different dimensions andsubstantially different ranges of motion. The invention is only limitedby the claims. It may be desirable to use different dimensions anddifferent ranges of motion to adapt the invention for needs ofparticular types of surgeries which have particular requirements for therange of motion of the insertion axis and for the space occupied by thedevice through its range of motion.

It is to be understood that the inventive parallel spherical five-barlinkage may be embodied in both powered and unpowered configurations. Inpowered embodiments, devices such as servo motors rotate the inboardlinks. The parallel spherical five-bar linkage translates thoserotations into two dimensional movement of the outboard axis. Inunpowered embodiments, two dimensional movement of the outboard axis istranslated by the parallel spherical five-bar linkage into rotations ofthe inboard links. Devices such as rotary encoders may sense thebearings of the inboard links and that information may be used tocompute the position of the outboard axis. Constraining the rotation ofan intermediate axis as previously described is advantageous inunpowered embodiments because the constraint limits the position of theoutboard axis to one of the two possible positions that correspond tothe bearings of the inboard links.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art. Instead, the embodimentsof the invention should be construed according to the claims that followbelow.

What is claimed is:
 1. A method for posing a robotic arm including aparallel spherical five-bar linkage in a minimally invasive surgicalsystem, the method comprising: pivotally coupling each of two inboardlinks to opposing ends of a ground link; pivotally coupling two outboardlinks respectively to the two inboard links; pivotally coupling twooutboard links together at an outboard axis; rotating the two inboardlinks to cross over one another.
 2. The method of claim 1, furthercomprising supporting an endoscopic camera by at least one of the twooutboard links.
 3. The method of claim 1, further comprising: rotating afirst one of the two inboard links with a first motor; rotating a secondone of the two inboard links with a second motor; and controlling thefirst and second motors to pose the five-bar spherical linkage in onlythe range of compact poses in which the two inboard links cross over oneanother.
 4. The method of claim 1, further comprising coupling amechanical stop to the two outboard links to maintain a minimum angle offifteen degrees between them.
 5. The method of claim 1, furthercomprising coupling the ground link to a table to support the roboticarm over a patient.
 6. The method of claim 1, further comprisingcoupling the ground link to a set-up arm to support the robotic arm overa patient.
 7. A method for posing a robotic arm that includes a parallelfive-bar spherical linkage to spherically rotationally move anendoscopic camera coupled to the parallel five-bar spherical linkageabout a remote center of spherical rotation in a minimally invasivesurgical system, the method comprising: pivotally coupling a firstinboard link and a first outboard link in the five-bar spherical linkageat a first intermediate joint; coupling the first inboard link to afirst end of a ground link in the five-bar spherical linkage; pivotallycoupling a second inboard link and a second outboard link in thefive-bar spherical linkage at a second intermediate joint; coupling thesecond inboard link to a second end of the ground link; pivotallycoupling the first outboard link to the second outboard link to form anoutboard joint; and posing the five-bar spherical linkage in a compactpose with the second inboard link crossing the first inboard link. 8.The method of claim 7, further comprising: rotating the first inboardlink to a first position; and rotating the second inboard link to asecond position such that the second inboard link crosses the firstinboard link.
 9. The method of claim 7, further comprising: fixing afirst motor to the first end of the ground link; coupling the firstmotor to the first inboard link; rotating the first inboard link withthe first motor to a first position; fixing a second motor to the secondend of the ground link; coupling the second motor to the second inboardlink; and rotating the second inboard link with the second motor suchthat the second inboard link crosses the first inboard link.
 10. Themethod of claim 7, further comprising coupling the ground link to atable to support the robotic arm over a patient.
 11. The method of claim7, further comprising coupling the ground link to a table with a set-uparm to support the robotic arm over a patient.
 12. The method of claim7, further comprising supporting the endoscopic camera by at least oneof the two outboard links.
 13. The method of claim 7, further comprisingcoupling a mechanical stop to the first outboard link to maintain aminimum angle of fifteen degrees between the first outboard link and thesecond outboard link.